The present invention relates to the semiconductor art, and more particularly to a container for semiconductor chips which container is capable of storing and transporting the semiconductor chips separated from a semiconductor wafer without causing disarrangement of the semiconductor chips.
In general, a number of semiconductor elements, such as transistors and integrated circuits, arranged in a scored grid-like pattern on a semiconductor wafer are formed in the wafer through known processes such as impurity diffusion, metal evaporation, selective etching and other processes, separated into individual chips, and then encased in semiconductor cases to provide semiconductor devices. One known method for breaking the chips from the wafer, is disclosed in U.S. Pat. No. 3,040,489 to Costa. This patent discloses a semiconductor dicing or breaking technique in which a semiconductor wafer, scribed on the surface thereof by a diamond scriber, is sandwiched by two cellophane sheets and then broken into individual chips by a steel or bronze roller. The dicing or breaking technique using an adhesive polyvinyl chloride film instead of the cellophane sheets of Costa has been proposed in Japanese Patent Publication No. 41-10372 published on June 6, 1966 by Nippon Electric Co., Ltd. Y. Nakamura, one of the inventors of the present invention has proposed, in Japanese Patent Publication No. 48-26420 published on Aug. 10, 1973, a spreading technique in connection with the broken chips located on the polyvinyl chloride film. According to this technique the polyvinyl film is fixed at its periphery to a ring fixture, spread by inserting a cylindrical ring into the center hole of the ring fixture and then fixed to the cylindrical ring by a rubber band, while the polyvinyl chloride film is cut off from the ring fixture to separate the cylindrical ring carrying the chips from the ring fixture.
The inventor Y. Nakamura has also proposed a method of cleansing the broken chips for an automatic encasing process in non-examined Japanese Patent Application published on Apr. 27, 1977 under No. 52-52568. According to this cleansing method, the rear surface of the semiconductor wafer prior to scribing process is preliminarily bonded, under heating, to a certain plastic film such as polyvinyl chloride film containing a suitable amount of plasticizer. The wafer is then scribed along score lines, and broken and separated into individual chips. Pure water is then showered uniformly onto the surfaces of the chips to remove vaious contaminations on the surfaces of the chips, especially silicon dust produced during the scribing or breaking process. Therefore, the chips are dried by centrifugalization and transferred directly to an automatic encasing process.
When the cleaned elements are transferred directly to an automatic encasing process, the separated chips can be easily transferred by locating the breaking process and the automatic encasing process in the same space and continuously processing these steps. However, when the sites of these operations are remoted from each other or when the chips as separated must be stored for some reason (such as production control requirement etc.), or when the chips are sold before they are encased, it is necessary to provide a method and apparatus for storing or transporting the chips which method retains the purity of the chip during storage or transportation.
When storing the separated chips arranged on the plastic film, it is standard practice to employ, for example, a clean bench or the like. While such benches are useful for storing the separated chips, they are not suitable for transporting the separated chips. Thus, when the elements must be transported, it is conventional to remove the separated chips from the plastic film and then to place each of them into a clean case. This method is convenient for the purpose of transportation, but not recommendable because it involves a problem in keeping the chips clean and needs increased number of steps. By way of example, this method will inevitably introduce contamination into the chips during removal of the separated chips from the plastic film (with tweezers etc.) or due to foreign matters brought into contact with the surfaces of the chips during packaging of the chips into the respective cases. This method necessitates a tremendous number of steps. Alternatively, the chips may be transported in such a manner that plural number of chips are randomly charged in a bottle. This, however, is less recommendable not only because of inconvenience in the succeeding processes but because of breakage or flaw caused on elements due to collision between the chips during the transportation.